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Study Analyzes Risk of Developing Second Breast Cancer (dateline January 23, 2001)


A recent study conducted by Swedish researchers shows that among women with breast cancer, those diagnosed at a young age (in their thirties) are more likely to develop a second cancer in the other breast than women who are originally diagnosed with breast cancer at an older age. The researchers believe that genetic factors may play a role in breast cancers among young women. In the study, young women with a family history of breast cancer were more likely to develop a second breast cancer than those without a family history of the disease.

To determine whether a link between age or family history and the diagnosis of a second breast cancer exists, co-researcher Kari Hemminki, MD and his colleague analyzed medical records obtained from the national Swedish Family-Cancer Database. 72,092 of the women had been diagnosed with unilateral breast cancer (cancer in one breast) between 1976 and 1996, and 2,529 of those women (3.5%) were found to have developed contralateral breast cancer (cancer in the other breast) six months or longer after their initial breast cancer diagnosis.

The researchers found that women who were diagnosed with unilateral breast cancer between ages 30 and 34 were most likely to develop contralateral breast cancer compared with other age groups. In fact, the chances of developing a second breast cancer was 50 times higher than the risk for women in the same age group to develop a first breast cancer. However, the risk of developing a second breast cancer was lower among women 35 years of age, and lowest among women over 50 years of age.

Family history also played a role in the development of a second breast cancer. In the study, young women who reported at least one first-degree family member with breast cancer (mother or sister) were 1.5 times more likely to develop a second breast cancer than women without a similar family history of the disease. Therefore, the researchers suggest that genetic factors may be key in determining which young women diagnosed with breast cancer are at risk of contralateral breast cancer. These genetic factors may include mutations of the BRCA1 (breast cancer gene 1) or BRCA2 (breast cancer gene 2) genes or other genes.

The results of the study suggest that young women who have been diagnosed with breast cancer should be closely monitored by physicians, especially if they have a family history of breast cancer. In fact, previous studies have shown that younger women who have a family history of breast cancer may benefit from starting annual screening mammograms before age 40.

In a study published in the March 2000 issue of European Journal of Cancer, researchers found that women with two first-degree relatives who developed breast cancer by age 50 were at a 25% higher than average risk for breast cancer than women with this family history. According to the researchers, these women should follow stricter guidelines to help detect breast cancer early, such as more frequent physician-performed clinical breast exams and annual mammograms beginning at age 25.

Currently, the American Cancer Society recommends:

  • All women between 20 and 39 practice monthly breast self-exams and have a physician performed clinical breast exam at least every three years.
  • All women age 40 and older have annual screening mammograms, practice monthly breast self-exams, and have yearly clinical breast exams.

Researchers are also investigating methods to help prevent the development of a second breast cancer. Preliminary research has shown that a drug called fenretinide (a derivative of vitamin A) may help reduce the chances of a second breast cancer in pre-menopausal women. In a study published in a November 1999 issue of the Journal of the National Cancer Institute, pre-menopausal women who took fenretinide were less likely to develop breast cancer again in either breast. However, fenretinide does not seem to be effective in post-menopausal women. Further research is expected to further explore pre-menopausal breast cancers.

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